speedometer question

Ok, my speedometer has shot craps. This started a couple months back by occasionally dropping to zero then raising back to indicated speed. I know this car doesn't have a cable and is all electronic. The problem is that I just moved to Ohio from Arizona and can't find my little (kinda worthless :) Haynes manual so that I can maybe trace the wiring out and find what drives/affects the speedometer.

I don't think the speedometer it's self has gone bad because when I turn the key off it drops to negitive zero which tells me that mechanism is at least still breathing.

Does anyone have some insight to what ancilary items I can check/replace to maybe get this thing working again? Where is the ESS? This is an 88 Park avenue

Thanks a million, Don

Basically, you attach a scan tool and go for a test drive....you look for vehicle speed in ECM data......this data should match the speedometer......

Two things can happen:

One is the speedometer and the ECM speed data match exactly....by that I mean, when the speedometer goes to zero, the ECM speed data goes to zero, too.......If that happens, then you have a problem with either the speed sensor in the tranny, or the wiring harness between the sensor and the ECM.....

The other is, the speedometer drops to zero, but the ECM speed data reads true.....this means you have either a bad speedometer(cluster), bad connection at the cluster, or bad wiring between the cluster and the ECM(computer).....

While driving, hit the dash on top of the cluster....does it affect the speedometer?

Well that makes good since, thank you. I can most likely rent a scan tool from Autozone and give her a whirl. I pulled in tonight and checked the ECM connection and any other connection I could reach.

I'm at work so I'll give the dash a whack on the way home in a little bit. I'll keep you posted. :smokin:

Don

Problem solved. I discovered that where the wire pair terminates at the connector to the ESS the wires are completely bare and touching. What the heck would cause the insulation to completely rot off the wires? Anyway, for a quick fix I coated the two wires with RTV until I can get into NAPA for a replacement termination.

Thanks again, Don